fs/btrfs/ctree.c

   1 #include <stdio.h>
   2 #include <stdlib.h>
   3 #include "kerncompat.h"
   4 #include "radix-tree.h"
   5 #include "ctree.h"
   6 #include "disk-io.h"
   7 #include "print-tree.h"
   8
   9 static int split_node(struct btrfs_root *root, struct btrfs_path *path,
  10                       int level);
  11 static int split_leaf(struct btrfs_root *root, struct btrfs_path *path,
  12                       int data_size);
  13 static int push_node_left(struct btrfs_root *root, struct btrfs_buffer *dst,
  14                           struct btrfs_buffer *src);
  15 static int balance_node_right(struct btrfs_root *root,
  16                               struct btrfs_buffer *dst_buf,
  17                               struct btrfs_buffer *src_buf);
  18 static int del_ptr(struct btrfs_root *root, struct btrfs_path *path, int level,
  19                    int slot);
  20
  21 inline void btrfs_init_path(struct btrfs_path *p)
  22 {
  23         memset(p, 0, sizeof(*p));
  24 }
  25
  26 void btrfs_release_path(struct btrfs_root *root, struct btrfs_path *p)
  27 {
  28         int i;
  29         for (i = 0; i < BTRFS_MAX_LEVEL; i++) {
  30                 if (!p->nodes[i])
  31                         break;
  32                 btrfs_block_release(root, p->nodes[i]);
  33         }
  34         memset(p, 0, sizeof(*p));
  35 }
  36
  37 int btrfs_cow_block(struct btrfs_root *root,
  38                     struct btrfs_buffer *buf,
  39                     struct btrfs_buffer *parent,
  40                     int parent_slot,
  41                     struct btrfs_buffer **cow_ret)
  42 {
  43         struct btrfs_buffer *cow;
  44
  45         if (!list_empty(&buf->dirty)) {
  46                 *cow_ret = buf;
  47                 return 0;
  48         }
  49         cow = btrfs_alloc_free_block(root);
  50         memcpy(&cow->node, &buf->node, sizeof(buf->node));
  51         btrfs_set_header_blocknr(&cow->node.header, cow->blocknr);
  52         *cow_ret = cow;
  53         btrfs_inc_ref(root, buf);
  54         if (buf == root->node) {
  55                 root->node = cow;
  56                 cow->count++;
  57                 if (buf != root->commit_root)
  58                         btrfs_free_extent(root, buf->blocknr, 1);
  59                 btrfs_block_release(root, buf);
  60         } else {
  61                 btrfs_set_node_blockptr(&parent->node, parent_slot,
  62                                         cow->blocknr);
  63                 BUG_ON(list_empty(&parent->dirty));
  64                 btrfs_free_extent(root, buf->blocknr, 1);
  65         }
  66         btrfs_block_release(root, buf);
  67         return 0;
  68 }
  69
  70 /*
  71  * The leaf data grows from end-to-front in the node.
  72  * this returns the address of the start of the last item,
  73  * which is the stop of the leaf data stack
  74  */
  75 static inline unsigned int leaf_data_end(struct btrfs_leaf *leaf)
  76 {
  77         u32 nr = btrfs_header_nritems(&leaf->header);
  78         if (nr == 0)
  79                 return sizeof(leaf->data);
  80         return btrfs_item_offset(leaf->items + nr - 1);
  81 }
  82
  83 /*
  84  * The space between the end of the leaf items and
  85  * the start of the leaf data.  IOW, how much room
  86  * the leaf has left for both items and data
  87  */
  88 int btrfs_leaf_free_space(struct btrfs_leaf *leaf)
  89 {
  90         int data_end = leaf_data_end(leaf);
  91         int nritems = btrfs_header_nritems(&leaf->header);
  92         char *items_end = (char *)(leaf->items + nritems + 1);
  93         return (char *)(leaf->data + data_end) - (char *)items_end;
  94 }
  95
  96 /*
  97  * compare two keys in a memcmp fashion
  98  */
  99 int comp_keys(struct btrfs_disk_key *disk, struct btrfs_key *k2)
 100 {
 101         struct btrfs_key k1;
 102
 103         btrfs_disk_key_to_cpu(&k1, disk);
 104
 105         if (k1.objectid > k2->objectid)
 106                 return 1;
 107         if (k1.objectid < k2->objectid)
 108                 return -1;
 109         if (k1.flags > k2->flags)
 110                 return 1;
 111         if (k1.flags < k2->flags)
 112                 return -1;
 113         if (k1.offset > k2->offset)
 114                 return 1;
 115         if (k1.offset < k2->offset)
 116                 return -1;
 117         return 0;
 118 }
 119
 120 int check_node(struct btrfs_path *path, int level)
 121 {
 122         int i;
 123         struct btrfs_node *parent = NULL;
 124         struct btrfs_node *node = &path->nodes[level]->node;
 125         int parent_slot;
 126         u32 nritems = btrfs_header_nritems(&node->header);
 127
 128         if (path->nodes[level + 1])
 129                 parent = &path->nodes[level + 1]->node;
 130         parent_slot = path->slots[level + 1];
 131         BUG_ON(nritems == 0);
 132         if (parent) {
 133                 struct btrfs_disk_key *parent_key;
 134                 parent_key = &parent->keys[parent_slot];
 135                 BUG_ON(memcmp(parent_key, node->keys,
 136                               sizeof(struct btrfs_disk_key)));
 137                 BUG_ON(btrfs_node_blockptr(parent, parent_slot) !=
 138                        btrfs_header_blocknr(&node->header));
 139         }
 140         BUG_ON(nritems > NODEPTRS_PER_BLOCK);
 141         for (i = 0; nritems > 1 && i < nritems - 2; i++) {
 142                 struct btrfs_key cpukey;
 143                 btrfs_disk_key_to_cpu(&cpukey, &node->keys[i + 1]);
 144                 BUG_ON(comp_keys(&node->keys[i], &cpukey) >= 0);
 145         }
 146         return 0;
 147 }
 148
 149 int check_leaf(struct btrfs_path *path, int level)
 150 {
 151         int i;
 152         struct btrfs_leaf *leaf = &path->nodes[level]->leaf;
 153         struct btrfs_node *parent = NULL;
 154         int parent_slot;
 155         u32 nritems = btrfs_header_nritems(&leaf->header);
 156
 157         if (path->nodes[level + 1])
 158                 parent = &path->nodes[level + 1]->node;
 159         parent_slot = path->slots[level + 1];
 160         BUG_ON(btrfs_leaf_free_space(leaf) < 0);
 161
 162         if (nritems == 0)
 163                 return 0;
 164
 165         if (parent) {
 166                 struct btrfs_disk_key *parent_key;
 167                 parent_key = &parent->keys[parent_slot];
 168                 BUG_ON(memcmp(parent_key, &leaf->items[0].key,
 169                        sizeof(struct btrfs_disk_key)));
 170                 BUG_ON(btrfs_node_blockptr(parent, parent_slot) !=
 171                        btrfs_header_blocknr(&leaf->header));
 172         }
 173         for (i = 0; nritems > 1 && i < nritems - 2; i++) {
 174                 struct btrfs_key cpukey;
 175                 btrfs_disk_key_to_cpu(&cpukey, &leaf->items[i + 1].key);
 176                 BUG_ON(comp_keys(&leaf->items[i].key,
 177                                  &cpukey) >= 0);
 178                 BUG_ON(btrfs_item_offset(leaf->items + i) !=
 179                         btrfs_item_end(leaf->items + i + 1));
 180                 if (i == 0) {
 181                         BUG_ON(btrfs_item_offset(leaf->items + i) +
 182                                btrfs_item_size(leaf->items + i) !=
 183                                LEAF_DATA_SIZE);
 184                 }
 185         }
 186         return 0;
 187 }
 188
 189 int check_block(struct btrfs_path *path, int level)
 190 {
 191         if (level == 0)
 192                 return check_leaf(path, level);
 193         return check_node(path, level);
 194 }
 195
 196 /*
 197  * search for key in the array p.  items p are item_size apart
 198  * and there are 'max' items in p
 199  * the slot in the array is returned via slot, and it points to
 200  * the place where you would insert key if it is not found in
 201  * the array.
 202  *
 203  * slot may point to max if the key is bigger than all of the keys
 204  */
 205 int generic_bin_search(char *p, int item_size, struct btrfs_key *key,
 206                        int max, int *slot)
 207 {
 208         int low = 0;
 209         int high = max;
 210         int mid;
 211         int ret;
 212         struct btrfs_disk_key *tmp;
 213
 214         while(low < high) {
 215                 mid = (low + high) / 2;
 216                 tmp = (struct btrfs_disk_key *)(p + mid * item_size);
 217                 ret = comp_keys(tmp, key);
 218
 219                 if (ret < 0)
 220                         low = mid + 1;
 221                 else if (ret > 0)
 222                         high = mid;
 223                 else {
 224                         *slot = mid;
 225                         return 0;
 226                 }
 227         }
 228         *slot = low;
 229         return 1;
 230 }
 231
 232 /*
 233  * simple bin_search frontend that does the right thing for
 234  * leaves vs nodes
 235  */
 236 int bin_search(struct btrfs_node *c, struct btrfs_key *key, int *slot)
 237 {
 238         if (btrfs_is_leaf(c)) {
 239                 struct btrfs_leaf *l = (struct btrfs_leaf *)c;
 240                 return generic_bin_search((void *)l->items,
 241                                           sizeof(struct btrfs_item),
 242                                           key, btrfs_header_nritems(&c->header),
 243                                           slot);
 244         } else {
 245                 return generic_bin_search((void *)c->keys,
 246                                           sizeof(struct btrfs_disk_key),
 247                                           key, btrfs_header_nritems(&c->header),
 248                                           slot);
 249         }
 250         return -1;
 251 }
 252
 253 struct btrfs_buffer *read_node_slot(struct btrfs_root *root,
 254                                    struct btrfs_buffer *parent_buf,
 255                                    int slot)
 256 {
 257         struct btrfs_node *node = &parent_buf->node;
 258         if (slot < 0)
 259                 return NULL;
 260         if (slot >= btrfs_header_nritems(&node->header))
 261                 return NULL;
 262         return read_tree_block(root, btrfs_node_blockptr(node, slot));
 263 }
 264
 265 static int balance_level(struct btrfs_root *root, struct btrfs_path *path,
 266                         int level)
 267 {
 268         struct btrfs_buffer *right_buf;
 269         struct btrfs_buffer *mid_buf;
 270         struct btrfs_buffer *left_buf;
 271         struct btrfs_buffer *parent_buf = NULL;
 272         struct btrfs_node *right = NULL;
 273         struct btrfs_node *mid;
 274         struct btrfs_node *left = NULL;
 275         struct btrfs_node *parent = NULL;
 276         int ret = 0;
 277         int wret;
 278         int pslot;
 279         int orig_slot = path->slots[level];
 280         u64 orig_ptr;
 281
 282         if (level == 0)
 283                 return 0;
 284
 285         mid_buf = path->nodes[level];
 286         mid = &mid_buf->node;
 287         orig_ptr = btrfs_node_blockptr(mid, orig_slot);
 288
 289         if (level < BTRFS_MAX_LEVEL - 1)
 290                 parent_buf = path->nodes[level + 1];
 291         pslot = path->slots[level + 1];
 292
 293         if (!parent_buf) {
 294                 struct btrfs_buffer *child;
 295                 u64 blocknr = mid_buf->blocknr;
 296
 297                 if (btrfs_header_nritems(&mid->header) != 1)
 298                         return 0;
 299
 300                 /* promote the child to a root */
 301                 child = read_node_slot(root, mid_buf, 0);
 302                 BUG_ON(!child);
 303                 root->node = child;
 304                 path->nodes[level] = NULL;
 305                 /* once for the path */
 306                 btrfs_block_release(root, mid_buf);
 307                 /* once for the root ptr */
 308                 btrfs_block_release(root, mid_buf);
 309                 clean_tree_block(root, mid_buf);
 310                 return btrfs_free_extent(root, blocknr, 1);
 311         }
 312         parent = &parent_buf->node;
 313
 314         if (btrfs_header_nritems(&mid->header) > NODEPTRS_PER_BLOCK / 4)
 315                 return 0;
 316
 317         left_buf = read_node_slot(root, parent_buf, pslot - 1);
 318         right_buf = read_node_slot(root, parent_buf, pslot + 1);
 319
 320         /* first, try to make some room in the middle buffer */
 321         if (left_buf) {
 322                 btrfs_cow_block(root, left_buf, parent_buf,
 323                                 pslot - 1, &left_buf);
 324                 left = &left_buf->node;
 325                 orig_slot += btrfs_header_nritems(&left->header);
 326                 wret = push_node_left(root, left_buf, mid_buf);
 327                 if (wret < 0)
 328                         ret = wret;
 329         }
 330
 331         /*
 332          * then try to empty the right most buffer into the middle
 333          */
 334         if (right_buf) {
 335                 btrfs_cow_block(root, right_buf, parent_buf,
 336                                 pslot + 1, &right_buf);
 337                 right = &right_buf->node;
 338                 wret = push_node_left(root, mid_buf, right_buf);
 339                 if (wret < 0)
 340                         ret = wret;
 341                 if (btrfs_header_nritems(&right->header) == 0) {
 342                         u64 blocknr = right_buf->blocknr;
 343                         btrfs_block_release(root, right_buf);
 344                         clean_tree_block(root, right_buf);
 345                         right_buf = NULL;
 346                         right = NULL;
 347                         wret = del_ptr(root, path, level + 1, pslot + 1);
 348                         if (wret)
 349                                 ret = wret;
 350                         wret = btrfs_free_extent(root, blocknr, 1);
 351                         if (wret)
 352                                 ret = wret;
 353                 } else {
 354                         memcpy(parent->keys + pslot + 1, right->keys,
 355                                 sizeof(struct btrfs_disk_key));
 356                         BUG_ON(list_empty(&parent_buf->dirty));
 357                 }
 358         }
 359         if (btrfs_header_nritems(&mid->header) == 1) {
 360                 /*
 361                  * we're not allowed to leave a node with one item in the
 362                  * tree during a delete.  A deletion from lower in the tree
 363                  * could try to delete the only pointer in this node.
 364                  * So, pull some keys from the left.
 365                  * There has to be a left pointer at this point because
 366                  * otherwise we would have pulled some pointers from the
 367                  * right
 368                  */
 369                 BUG_ON(!left_buf);
 370                 wret = balance_node_right(root, mid_buf, left_buf);
 371                 if (wret < 0)
 372                         ret = wret;
 373                 BUG_ON(wret == 1);
 374         }
 375         if (btrfs_header_nritems(&mid->header) == 0) {
 376                 /* we've managed to empty the middle node, drop it */
 377                 u64 blocknr = mid_buf->blocknr;
 378                 btrfs_block_release(root, mid_buf);
 379                 clean_tree_block(root, mid_buf);
 380                 mid_buf = NULL;
 381                 mid = NULL;
 382                 wret = del_ptr(root, path, level + 1, pslot);
 383                 if (wret)
 384                         ret = wret;
 385                 wret = btrfs_free_extent(root, blocknr, 1);
 386                 if (wret)
 387                         ret = wret;
 388         } else {
 389                 /* update the parent key to reflect our changes */
 390                 memcpy(parent->keys + pslot, mid->keys,
 391                        sizeof(struct btrfs_disk_key));
 392                 BUG_ON(list_empty(&parent_buf->dirty));
 393         }
 394
 395         /* update the path */
 396         if (left_buf) {
 397                 if (btrfs_header_nritems(&left->header) > orig_slot) {
 398                         left_buf->count++; // released below
 399                         path->nodes[level] = left_buf;
 400                         path->slots[level + 1] -= 1;
 401                         path->slots[level] = orig_slot;
 402                         if (mid_buf)
 403                                 btrfs_block_release(root, mid_buf);
 404                 } else {
 405                         orig_slot -= btrfs_header_nritems(&left->header);
 406                         path->slots[level] = orig_slot;
 407                 }
 408         }
 409         /* double check we haven't messed things up */
 410         check_block(path, level);
 411         if (orig_ptr != btrfs_node_blockptr(&path->nodes[level]->node,
 412                                             path->slots[level]))
 413                 BUG();
 414
 415         if (right_buf)
 416                 btrfs_block_release(root, right_buf);
 417         if (left_buf)
 418                 btrfs_block_release(root, left_buf);
 419         return ret;
 420 }
 421
 422 /*
 423  * look for key in the tree.  path is filled in with nodes along the way
 424  * if key is found, we return zero and you can find the item in the leaf
 425  * level of the path (level 0)
 426  *
 427  * If the key isn't found, the path points to the slot where it should
 428  * be inserted, and 1 is returned.  If there are other errors during the
 429  * search a negative error number is returned.
 430  *
 431  * if ins_len > 0, nodes and leaves will be split as we walk down the
 432  * tree.  if ins_len < 0, nodes will be merged as we walk down the tree (if
 433  * possible)
 434  */
 435 int btrfs_search_slot(struct btrfs_root *root, struct btrfs_key *key,
 436                 struct btrfs_path *p, int ins_len, int cow)
 437 {
 438         struct btrfs_buffer *b;
 439         struct btrfs_buffer *cow_buf;
 440         struct btrfs_node *c;
 441         int slot;
 442         int ret;
 443         int level;
 444
 445 again:
 446         b = root->node;
 447         b->count++;
 448         while (b) {
 449                 level = btrfs_header_level(&b->node.header);
 450                 if (cow) {
 451                         int wret;
 452                         wret = btrfs_cow_block(root, b, p->nodes[level + 1],
 453                                                p->slots[level + 1], &cow_buf);
 454                         b = cow_buf;
 455                 }
 456                 BUG_ON(!cow && ins_len);
 457                 c = &b->node;
 458                 p->nodes[level] = b;
 459                 ret = check_block(p, level);
 460                 if (ret)
 461                         return -1;
 462                 ret = bin_search(c, key, &slot);
 463                 if (!btrfs_is_leaf(c)) {
 464                         if (ret && slot > 0)
 465                                 slot -= 1;
 466                         p->slots[level] = slot;
 467                         if (ins_len > 0 && btrfs_header_nritems(&c->header) ==
 468                             NODEPTRS_PER_BLOCK) {
 469                                 int sret = split_node(root, p, level);
 470                                 BUG_ON(sret > 0);
 471                                 if (sret)
 472                                         return sret;
 473                                 b = p->nodes[level];
 474                                 c = &b->node;
 475                                 slot = p->slots[level];
 476                         } else if (ins_len < 0) {
 477                                 int sret = balance_level(root, p, level);
 478                                 if (sret)
 479                                         return sret;
 480                                 b = p->nodes[level];
 481                                 if (!b)
 482                                         goto again;
 483                                 c = &b->node;
 484                                 slot = p->slots[level];
 485                                 BUG_ON(btrfs_header_nritems(&c->header) == 1);
 486                         }
 487                         b = read_tree_block(root, btrfs_node_blockptr(c, slot));
 488                 } else {
 489                         struct btrfs_leaf *l = (struct btrfs_leaf *)c;
 490                         p->slots[level] = slot;
 491                         if (ins_len > 0 && btrfs_leaf_free_space(l) <
 492                             sizeof(struct btrfs_item) + ins_len) {
 493                                 int sret = split_leaf(root, p, ins_len);
 494                                 BUG_ON(sret > 0);
 495                                 if (sret)
 496                                         return sret;
 497                         }
 498                         BUG_ON(root->node->count == 1);
 499                         return ret;
 500                 }
 501         }
 502         BUG_ON(root->node->count == 1);
 503         return 1;
 504 }
 505
 506 /*
 507  * adjust the pointers going up the tree, starting at level
 508  * making sure the right key of each node is points to 'key'.
 509  * This is used after shifting pointers to the left, so it stops
 510  * fixing up pointers when a given leaf/node is not in slot 0 of the
 511  * higher levels
 512  *
 513  * If this fails to write a tree block, it returns -1, but continues
 514  * fixing up the blocks in ram so the tree is consistent.
 515  */
 516 static int fixup_low_keys(struct btrfs_root *root,
 517                            struct btrfs_path *path, struct btrfs_disk_key *key,
 518                            int level)
 519 {
 520         int i;
 521         int ret = 0;
 522         for (i = level; i < BTRFS_MAX_LEVEL; i++) {
 523                 struct btrfs_node *t;
 524                 int tslot = path->slots[i];
 525                 if (!path->nodes[i])
 526                         break;
 527                 t = &path->nodes[i]->node;
 528                 memcpy(t->keys + tslot, key, sizeof(*key));
 529                 BUG_ON(list_empty(&path->nodes[i]->dirty));
 530                 if (tslot != 0)
 531                         break;
 532         }
 533         return ret;
 534 }
 535
 536 /*
 537  * try to push data from one node into the next node left in the
 538  * tree.
 539  *
 540  * returns 0 if some ptrs were pushed left, < 0 if there was some horrible
 541  * error, and > 0 if there was no room in the left hand block.
 542  */
 543 static int push_node_left(struct btrfs_root *root, struct btrfs_buffer *dst_buf,
 544                           struct btrfs_buffer *src_buf)
 545 {
 546         struct btrfs_node *src = &src_buf->node;
 547         struct btrfs_node *dst = &dst_buf->node;
 548         int push_items = 0;
 549         int src_nritems;
 550         int dst_nritems;
 551         int ret = 0;
 552
 553         src_nritems = btrfs_header_nritems(&src->header);
 554         dst_nritems = btrfs_header_nritems(&dst->header);
 555         push_items = NODEPTRS_PER_BLOCK - dst_nritems;
 556         if (push_items <= 0) {
 557                 return 1;
 558         }
 559
 560         if (src_nritems < push_items)
 561                 push_items = src_nritems;
 562
 563         memcpy(dst->keys + dst_nritems, src->keys,
 564                 push_items * sizeof(struct btrfs_disk_key));
 565         memcpy(dst->blockptrs + dst_nritems, src->blockptrs,
 566                 push_items * sizeof(u64));
 567         if (push_items < src_nritems) {
 568                 memmove(src->keys, src->keys + push_items,
 569                         (src_nritems - push_items) *
 570                         sizeof(struct btrfs_disk_key));
 571                 memmove(src->blockptrs, src->blockptrs + push_items,
 572                         (src_nritems - push_items) * sizeof(u64));
 573         }
 574         btrfs_set_header_nritems(&src->header, src_nritems - push_items);
 575         btrfs_set_header_nritems(&dst->header, dst_nritems + push_items);
 576         BUG_ON(list_empty(&src_buf->dirty));
 577         BUG_ON(list_empty(&dst_buf->dirty));
 578         return ret;
 579 }
 580
 581 /*
 582  * try to push data from one node into the next node right in the
 583  * tree.
 584  *
 585  * returns 0 if some ptrs were pushed, < 0 if there was some horrible
 586  * error, and > 0 if there was no room in the right hand block.
 587  *
 588  * this will  only push up to 1/2 the contents of the left node over
 589  */
 590 static int balance_node_right(struct btrfs_root *root,
 591                               struct btrfs_buffer *dst_buf,
 592                               struct btrfs_buffer *src_buf)
 593 {
 594         struct btrfs_node *src = &src_buf->node;
 595         struct btrfs_node *dst = &dst_buf->node;
 596         int push_items = 0;
 597         int max_push;
 598         int src_nritems;
 599         int dst_nritems;
 600         int ret = 0;
 601
 602         src_nritems = btrfs_header_nritems(&src->header);
 603         dst_nritems = btrfs_header_nritems(&dst->header);
 604         push_items = NODEPTRS_PER_BLOCK - dst_nritems;
 605         if (push_items <= 0) {
 606                 return 1;
 607         }
 608
 609         max_push = src_nritems / 2 + 1;
 610         /* don't try to empty the node */
 611         if (max_push > src_nritems)
 612                 return 1;
 613         if (max_push < push_items)
 614                 push_items = max_push;
 615
 616         memmove(dst->keys + push_items, dst->keys,
 617                 dst_nritems * sizeof(struct btrfs_disk_key));
 618         memmove(dst->blockptrs + push_items, dst->blockptrs,
 619                 dst_nritems * sizeof(u64));
 620         memcpy(dst->keys, src->keys + src_nritems - push_items,
 621                 push_items * sizeof(struct btrfs_disk_key));
 622         memcpy(dst->blockptrs, src->blockptrs + src_nritems - push_items,
 623                 push_items * sizeof(u64));
 624
 625         btrfs_set_header_nritems(&src->header, src_nritems - push_items);
 626         btrfs_set_header_nritems(&dst->header, dst_nritems + push_items);
 627
 628         BUG_ON(list_empty(&src_buf->dirty));
 629         BUG_ON(list_empty(&dst_buf->dirty));
 630         return ret;
 631 }
 632
 633 /*
 634  * helper function to insert a new root level in the tree.
 635  * A new node is allocated, and a single item is inserted to
 636  * point to the existing root
 637  *
 638  * returns zero on success or < 0 on failure.
 639  */
 640 static int insert_new_root(struct btrfs_root *root,
 641                            struct btrfs_path *path, int level)
 642 {
 643         struct btrfs_buffer *t;
 644         struct btrfs_node *lower;
 645         struct btrfs_node *c;
 646         struct btrfs_disk_key *lower_key;
 647
 648         BUG_ON(path->nodes[level]);
 649         BUG_ON(path->nodes[level-1] != root->node);
 650
 651         t = btrfs_alloc_free_block(root);
 652         c = &t->node;
 653         memset(c, 0, sizeof(c));
 654         btrfs_set_header_nritems(&c->header, 1);
 655         btrfs_set_header_level(&c->header, level);
 656         btrfs_set_header_blocknr(&c->header, t->blocknr);
 657         btrfs_set_header_parentid(&c->header,
 658                                btrfs_header_parentid(&root->node->node.header));
 659         lower = &path->nodes[level-1]->node;
 660         if (btrfs_is_leaf(lower))
 661                 lower_key = &((struct btrfs_leaf *)lower)->items[0].key;
 662         else
 663                 lower_key = lower->keys;
 664         memcpy(c->keys, lower_key, sizeof(struct btrfs_disk_key));
 665         btrfs_set_node_blockptr(c, 0, path->nodes[level - 1]->blocknr);
 666         /* the super has an extra ref to root->node */
 667         btrfs_block_release(root, root->node);
 668         root->node = t;
 669         t->count++;
 670         path->nodes[level] = t;
 671         path->slots[level] = 0;
 672         return 0;
 673 }
 674
 675 /*
 676  * worker function to insert a single pointer in a node.
 677  * the node should have enough room for the pointer already
 678  *
 679  * slot and level indicate where you want the key to go, and
 680  * blocknr is the block the key points to.
 681  *
 682  * returns zero on success and < 0 on any error
 683  */
 684 static int insert_ptr(struct btrfs_root *root,
 685                 struct btrfs_path *path, struct btrfs_disk_key *key,
 686                 u64 blocknr, int slot, int level)
 687 {
 688         struct btrfs_node *lower;
 689         int nritems;
 690
 691         BUG_ON(!path->nodes[level]);
 692         lower = &path->nodes[level]->node;
 693         nritems = btrfs_header_nritems(&lower->header);
 694         if (slot > nritems)
 695                 BUG();
 696         if (nritems == NODEPTRS_PER_BLOCK)
 697                 BUG();
 698         if (slot != nritems) {
 699                 memmove(lower->keys + slot + 1, lower->keys + slot,
 700                         (nritems - slot) * sizeof(struct btrfs_disk_key));
 701                 memmove(lower->blockptrs + slot + 1, lower->blockptrs + slot,
 702                         (nritems - slot) * sizeof(u64));
 703         }
 704         memcpy(lower->keys + slot, key, sizeof(struct btrfs_disk_key));
 705         btrfs_set_node_blockptr(lower, slot, blocknr);
 706         btrfs_set_header_nritems(&lower->header, nritems + 1);
 707         if (lower->keys[1].objectid == 0)
 708                         BUG();
 709         BUG_ON(list_empty(&path->nodes[level]->dirty));
 710         return 0;
 711 }
 712
 713 /*
 714  * split the node at the specified level in path in two.
 715  * The path is corrected to point to the appropriate node after the split
 716  *
 717  * Before splitting this tries to make some room in the node by pushing
 718  * left and right, if either one works, it returns right away.
 719  *
 720  * returns 0 on success and < 0 on failure
 721  */
 722 static int split_node(struct btrfs_root *root, struct btrfs_path *path,
 723                       int level)
 724 {
 725         struct btrfs_buffer *t;
 726         struct btrfs_node *c;
 727         struct btrfs_buffer *split_buffer;
 728         struct btrfs_node *split;
 729         int mid;
 730         int ret;
 731         int wret;
 732         u32 c_nritems;
 733
 734         t = path->nodes[level];
 735         c = &t->node;
 736         if (t == root->node) {
 737                 /* trying to split the root, lets make a new one */
 738                 ret = insert_new_root(root, path, level + 1);
 739                 if (ret)
 740                         return ret;
 741         }
 742         c_nritems = btrfs_header_nritems(&c->header);
 743         split_buffer = btrfs_alloc_free_block(root);
 744         split = &split_buffer->node;
 745         btrfs_set_header_flags(&split->header, btrfs_header_flags(&c->header));
 746         btrfs_set_header_blocknr(&split->header, split_buffer->blocknr);
 747         btrfs_set_header_parentid(&split->header,
 748                                btrfs_header_parentid(&root->node->node.header));
 749         mid = (c_nritems + 1) / 2;
 750         memcpy(split->keys, c->keys + mid,
 751                 (c_nritems - mid) * sizeof(struct btrfs_disk_key));
 752         memcpy(split->blockptrs, c->blockptrs + mid,
 753                 (c_nritems - mid) * sizeof(u64));
 754         btrfs_set_header_nritems(&split->header, c_nritems - mid);
 755         btrfs_set_header_nritems(&c->header, mid);
 756         ret = 0;
 757
 758         BUG_ON(list_empty(&t->dirty));
 759         wret = insert_ptr(root, path, split->keys, split_buffer->blocknr,
 760                           path->slots[level + 1] + 1, level + 1);
 761         if (wret)
 762                 ret = wret;
 763
 764         if (path->slots[level] >= mid) {
 765                 path->slots[level] -= mid;
 766                 btrfs_block_release(root, t);
 767                 path->nodes[level] = split_buffer;
 768                 path->slots[level + 1] += 1;
 769         } else {
 770                 btrfs_block_release(root, split_buffer);
 771         }
 772         return ret;
 773 }
 774
 775 /*
 776  * how many bytes are required to store the items in a leaf.  start
 777  * and nr indicate which items in the leaf to check.  This totals up the
 778  * space used both by the item structs and the item data
 779  */
 780 static int leaf_space_used(struct btrfs_leaf *l, int start, int nr)
 781 {
 782         int data_len;
 783         int end = start + nr - 1;
 784
 785         if (!nr)
 786                 return 0;
 787         data_len = btrfs_item_end(l->items + start);
 788         data_len = data_len - btrfs_item_offset(l->items + end);
 789         data_len += sizeof(struct btrfs_item) * nr;
 790         return data_len;
 791 }
 792
 793 /*
 794  * push some data in the path leaf to the right, trying to free up at
 795  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
 796  *
 797  * returns 1 if the push failed because the other node didn't have enough
 798  * room, 0 if everything worked out and < 0 if there were major errors.
 799  */
 800 static int push_leaf_right(struct btrfs_root *root, struct btrfs_path *path,
 801                            int data_size)
 802 {
 803         struct btrfs_buffer *left_buf = path->nodes[0];
 804         struct btrfs_leaf *left = &left_buf->leaf;
 805         struct btrfs_leaf *right;
 806         struct btrfs_buffer *right_buf;
 807         struct btrfs_buffer *upper;
 808         int slot;
 809         int i;
 810         int free_space;
 811         int push_space = 0;
 812         int push_items = 0;
 813         struct btrfs_item *item;
 814         u32 left_nritems;
 815         u32 right_nritems;
 816
 817         slot = path->slots[1];
 818         if (!path->nodes[1]) {
 819                 return 1;
 820         }
 821         upper = path->nodes[1];
 822         if (slot >= btrfs_header_nritems(&upper->node.header) - 1) {
 823                 return 1;
 824         }
 825         right_buf = read_tree_block(root, btrfs_node_blockptr(&upper->node,
 826                                                               slot + 1));
 827         right = &right_buf->leaf;
 828         free_space = btrfs_leaf_free_space(right);
 829         if (free_space < data_size + sizeof(struct btrfs_item)) {
 830                 btrfs_block_release(root, right_buf);
 831                 return 1;
 832         }
 833         /* cow and double check */
 834         btrfs_cow_block(root, right_buf, upper, slot + 1, &right_buf);
 835         right = &right_buf->leaf;
 836         free_space = btrfs_leaf_free_space(right);
 837         if (free_space < data_size + sizeof(struct btrfs_item)) {
 838                 btrfs_block_release(root, right_buf);
 839                 return 1;
 840         }
 841
 842         left_nritems = btrfs_header_nritems(&left->header);
 843         for (i = left_nritems - 1; i >= 0; i--) {
 844                 item = left->items + i;
 845                 if (path->slots[0] == i)
 846                         push_space += data_size + sizeof(*item);
 847                 if (btrfs_item_size(item) + sizeof(*item) + push_space >
 848                     free_space)
 849                         break;
 850                 push_items++;
 851                 push_space += btrfs_item_size(item) + sizeof(*item);
 852         }
 853         if (push_items == 0) {
 854                 btrfs_block_release(root, right_buf);
 855                 return 1;
 856         }
 857         right_nritems = btrfs_header_nritems(&right->header);
 858         /* push left to right */
 859         push_space = btrfs_item_end(left->items + left_nritems - push_items);
 860         push_space -= leaf_data_end(left);
 861         /* make room in the right data area */
 862         memmove(right->data + leaf_data_end(right) - push_space,
 863                 right->data + leaf_data_end(right),
 864                 LEAF_DATA_SIZE - leaf_data_end(right));
 865         /* copy from the left data area */
 866         memcpy(right->data + LEAF_DATA_SIZE - push_space,
 867                 left->data + leaf_data_end(left),
 868                 push_space);
 869         memmove(right->items + push_items, right->items,
 870                 right_nritems * sizeof(struct btrfs_item));
 871         /* copy the items from left to right */
 872         memcpy(right->items, left->items + left_nritems - push_items,
 873                 push_items * sizeof(struct btrfs_item));
 874
 875         /* update the item pointers */
 876         right_nritems += push_items;
 877         btrfs_set_header_nritems(&right->header, right_nritems);
 878         push_space = LEAF_DATA_SIZE;
 879         for (i = 0; i < right_nritems; i++) {
 880                 btrfs_set_item_offset(right->items + i, push_space -
 881                                       btrfs_item_size(right->items + i));
 882                 push_space = btrfs_item_offset(right->items + i);
 883         }
 884         left_nritems -= push_items;
 885         btrfs_set_header_nritems(&left->header, left_nritems);
 886
 887         BUG_ON(list_empty(&left_buf->dirty));
 888         BUG_ON(list_empty(&right_buf->dirty));
 889         memcpy(upper->node.keys + slot + 1,
 890                 &right->items[0].key, sizeof(struct btrfs_disk_key));
 891         BUG_ON(list_empty(&upper->dirty));
 892
 893         /* then fixup the leaf pointer in the path */
 894         if (path->slots[0] >= left_nritems) {
 895                 path->slots[0] -= left_nritems;
 896                 btrfs_block_release(root, path->nodes[0]);
 897                 path->nodes[0] = right_buf;
 898                 path->slots[1] += 1;
 899         } else {
 900                 btrfs_block_release(root, right_buf);
 901         }
 902         return 0;
 903 }
 904 /*
 905  * push some data in the path leaf to the left, trying to free up at
 906  * least data_size bytes.  returns zero if the push worked, nonzero otherwise
 907  */
 908 static int push_leaf_left(struct btrfs_root *root, struct btrfs_path *path,
 909                           int data_size)
 910 {
 911         struct btrfs_buffer *right_buf = path->nodes[0];
 912         struct btrfs_leaf *right = &right_buf->leaf;
 913         struct btrfs_buffer *t;
 914         struct btrfs_leaf *left;
 915         int slot;
 916         int i;
 917         int free_space;
 918         int push_space = 0;
 919         int push_items = 0;
 920         struct btrfs_item *item;
 921         u32 old_left_nritems;
 922         int ret = 0;
 923         int wret;
 924
 925         slot = path->slots[1];
 926         if (slot == 0) {
 927                 return 1;
 928         }
 929         if (!path->nodes[1]) {
 930                 return 1;
 931         }
 932         t = read_tree_block(root, btrfs_node_blockptr(&path->nodes[1]->node,
 933                                                       slot - 1));
 934         left = &t->leaf;
 935         free_space = btrfs_leaf_free_space(left);
 936         if (free_space < data_size + sizeof(struct btrfs_item)) {
 937                 btrfs_block_release(root, t);
 938                 return 1;
 939         }
 940
 941         /* cow and double check */
 942         btrfs_cow_block(root, t, path->nodes[1], slot - 1, &t);
 943         left = &t->leaf;
 944         free_space = btrfs_leaf_free_space(left);
 945         if (free_space < data_size + sizeof(struct btrfs_item)) {
 946                 btrfs_block_release(root, t);
 947                 return 1;
 948         }
 949
 950         for (i = 0; i < btrfs_header_nritems(&right->header); i++) {
 951                 item = right->items + i;
 952                 if (path->slots[0] == i)
 953                         push_space += data_size + sizeof(*item);
 954                 if (btrfs_item_size(item) + sizeof(*item) + push_space >
 955                     free_space)
 956                         break;
 957                 push_items++;
 958                 push_space += btrfs_item_size(item) + sizeof(*item);
 959         }
 960         if (push_items == 0) {
 961                 btrfs_block_release(root, t);
 962                 return 1;
 963         }
 964         /* push data from right to left */
 965         memcpy(left->items + btrfs_header_nritems(&left->header),
 966                 right->items, push_items * sizeof(struct btrfs_item));
 967         push_space = LEAF_DATA_SIZE -
 968                      btrfs_item_offset(right->items + push_items -1);
 969         memcpy(left->data + leaf_data_end(left) - push_space,
 970                 right->data + btrfs_item_offset(right->items + push_items - 1),
 971                 push_space);
 972         old_left_nritems = btrfs_header_nritems(&left->header);
 973         BUG_ON(old_left_nritems < 0);
 974
 975         for (i = old_left_nritems; i < old_left_nritems + push_items; i++) {
 976                 u16 ioff = btrfs_item_offset(left->items + i);
 977                 btrfs_set_item_offset(left->items + i, ioff - (LEAF_DATA_SIZE -
 978                                       btrfs_item_offset(left->items +
 979                                                         old_left_nritems - 1)));
 980         }
 981         btrfs_set_header_nritems(&left->header, old_left_nritems + push_items);
 982
 983         /* fixup right node */
 984         push_space = btrfs_item_offset(right->items + push_items - 1) -
 985                      leaf_data_end(right);
 986         memmove(right->data + LEAF_DATA_SIZE - push_space, right->data +
 987                 leaf_data_end(right), push_space);
 988         memmove(right->items, right->items + push_items,
 989                 (btrfs_header_nritems(&right->header) - push_items) *
 990                 sizeof(struct btrfs_item));
 991         btrfs_set_header_nritems(&right->header,
 992                                  btrfs_header_nritems(&right->header) -
 993                                  push_items);
 994         push_space = LEAF_DATA_SIZE;
 995
 996         for (i = 0; i < btrfs_header_nritems(&right->header); i++) {
 997                 btrfs_set_item_offset(right->items + i, push_space -
 998                                       btrfs_item_size(right->items + i));
 999                 push_space = btrfs_item_offset(right->items + i);
1000         }
1001
1002         BUG_ON(list_empty(&t->dirty));
1003         BUG_ON(list_empty(&right_buf->dirty));
1004
1005         wret = fixup_low_keys(root, path, &right->items[0].key, 1);
1006         if (wret)
1007                 ret = wret;
1008
1009         /* then fixup the leaf pointer in the path */
1010         if (path->slots[0] < push_items) {
1011                 path->slots[0] += old_left_nritems;
1012                 btrfs_block_release(root, path->nodes[0]);
1013                 path->nodes[0] = t;
1014                 path->slots[1] -= 1;
1015         } else {
1016                 btrfs_block_release(root, t);
1017                 path->slots[0] -= push_items;
1018         }
1019         BUG_ON(path->slots[0] < 0);
1020         return ret;
1021 }
1022
1023 /*
1024  * split the path's leaf in two, making sure there is at least data_size
1025  * available for the resulting leaf level of the path.
1026  *
1027  * returns 0 if all went well and < 0 on failure.
1028  */
1029 static int split_leaf(struct btrfs_root *root, struct btrfs_path *path,
1030                       int data_size)
1031 {
1032         struct btrfs_buffer *l_buf;
1033         struct btrfs_leaf *l;
1034         u32 nritems;
1035         int mid;
1036         int slot;
1037         struct btrfs_leaf *right;
1038         struct btrfs_buffer *right_buffer;
1039         int space_needed = data_size + sizeof(struct btrfs_item);
1040         int data_copy_size;
1041         int rt_data_off;
1042         int i;
1043         int ret;
1044         int wret;
1045
1046         l_buf = path->nodes[0];
1047         l = &l_buf->leaf;
1048
1049         /* did the pushes work? */
1050         if (btrfs_leaf_free_space(l) >= sizeof(struct btrfs_item) + data_size)
1051                 return 0;
1052
1053         if (!path->nodes[1]) {
1054                 ret = insert_new_root(root, path, 1);
1055                 if (ret)
1056                         return ret;
1057         }
1058         slot = path->slots[0];
1059         nritems = btrfs_header_nritems(&l->header);
1060         mid = (nritems + 1)/ 2;
1061         right_buffer = btrfs_alloc_free_block(root);
1062         BUG_ON(!right_buffer);
1063         BUG_ON(mid == nritems);
1064         right = &right_buffer->leaf;
1065         memset(right, 0, sizeof(*right));
1066         if (mid <= slot) {
1067                 /* FIXME, just alloc a new leaf here */
1068                 if (leaf_space_used(l, mid, nritems - mid) + space_needed >
1069                         LEAF_DATA_SIZE)
1070                         BUG();
1071         } else {
1072                 /* FIXME, just alloc a new leaf here */
1073                 if (leaf_space_used(l, 0, mid + 1) + space_needed >
1074                         LEAF_DATA_SIZE)
1075                         BUG();
1076         }
1077         btrfs_set_header_nritems(&right->header, nritems - mid);
1078         btrfs_set_header_blocknr(&right->header, right_buffer->blocknr);
1079         btrfs_set_header_level(&right->header, 0);
1080         btrfs_set_header_parentid(&right->header,
1081                                btrfs_header_parentid(&root->node->node.header));
1082         data_copy_size = btrfs_item_end(l->items + mid) - leaf_data_end(l);
1083         memcpy(right->items, l->items + mid,
1084                (nritems - mid) * sizeof(struct btrfs_item));
1085         memcpy(right->data + LEAF_DATA_SIZE - data_copy_size,
1086                l->data + leaf_data_end(l), data_copy_size);
1087         rt_data_off = LEAF_DATA_SIZE - btrfs_item_end(l->items + mid);
1088
1089         for (i = 0; i < btrfs_header_nritems(&right->header); i++) {
1090                 u16 ioff = btrfs_item_offset(right->items + i);
1091                 btrfs_set_item_offset(right->items + i, ioff + rt_data_off);
1092         }
1093
1094         btrfs_set_header_nritems(&l->header, mid);
1095         ret = 0;
1096         wret = insert_ptr(root, path, &right->items[0].key,
1097                           right_buffer->blocknr, path->slots[1] + 1, 1);
1098         if (wret)
1099                 ret = wret;
1100         BUG_ON(list_empty(&right_buffer->dirty));
1101         BUG_ON(list_empty(&l_buf->dirty));
1102         BUG_ON(path->slots[0] != slot);
1103         if (mid <= slot) {
1104                 btrfs_block_release(root, path->nodes[0]);
1105                 path->nodes[0] = right_buffer;
1106                 path->slots[0] -= mid;
1107                 path->slots[1] += 1;
1108         } else
1109                 btrfs_block_release(root, right_buffer);
1110         BUG_ON(path->slots[0] < 0);
1111         return ret;
1112 }
1113
1114 /*
1115  * Given a key and some data, insert an item into the tree.
1116  * This does all the path init required, making room in the tree if needed.
1117  */
1118 int btrfs_insert_item(struct btrfs_root *root, struct btrfs_key *cpu_key,
1119                           void *data, int data_size)
1120 {
1121         int ret = 0;
1122         int slot;
1123         int slot_orig;
1124         struct btrfs_leaf *leaf;
1125         struct btrfs_buffer *leaf_buf;
1126         u32 nritems;
1127         unsigned int data_end;
1128         struct btrfs_path path;
1129         struct btrfs_disk_key disk_key;
1130
1131         btrfs_cpu_key_to_disk(&disk_key, cpu_key);
1132
1133         /* create a root if there isn't one */
1134         if (!root->node)
1135                 BUG();
1136         btrfs_init_path(&path);
1137         ret = btrfs_search_slot(root, cpu_key, &path, data_size, 1);
1138         if (ret == 0) {
1139                 btrfs_release_path(root, &path);
1140                 return -EEXIST;
1141         }
1142         if (ret < 0)
1143                 goto out;
1144
1145         slot_orig = path.slots[0];
1146         leaf_buf = path.nodes[0];
1147         leaf = &leaf_buf->leaf;
1148
1149         nritems = btrfs_header_nritems(&leaf->header);
1150         data_end = leaf_data_end(leaf);
1151
1152         if (btrfs_leaf_free_space(leaf) <
1153             sizeof(struct btrfs_item) + data_size)
1154                 BUG();
1155
1156         slot = path.slots[0];
1157         BUG_ON(slot < 0);
1158         if (slot != nritems) {
1159                 int i;
1160                 unsigned int old_data = btrfs_item_end(leaf->items + slot);
1161
1162                 /*
1163                  * item0..itemN ... dataN.offset..dataN.size .. data0.size
1164                  */
1165                 /* first correct the data pointers */
1166                 for (i = slot; i < nritems; i++) {
1167                         u16 ioff = btrfs_item_offset(leaf->items + i);
1168                         btrfs_set_item_offset(leaf->items + i,
1169                                               ioff - data_size);
1170                 }
1171
1172                 /* shift the items */
1173                 memmove(leaf->items + slot + 1, leaf->items + slot,
1174                         (nritems - slot) * sizeof(struct btrfs_item));
1175
1176                 /* shift the data */
1177                 memmove(leaf->data + data_end - data_size, leaf->data +
1178                         data_end, old_data - data_end);
1179                 data_end = old_data;
1180         }
1181         /* copy the new data in */
1182         memcpy(&leaf->items[slot].key, &disk_key,
1183                 sizeof(struct btrfs_disk_key));
1184         btrfs_set_item_offset(leaf->items + slot, data_end - data_size);
1185         btrfs_set_item_size(leaf->items + slot, data_size);
1186         memcpy(leaf->data + data_end - data_size, data, data_size);
1187         btrfs_set_header_nritems(&leaf->header, nritems + 1);
1188
1189         ret = 0;
1190         if (slot == 0)
1191                 ret = fixup_low_keys(root, &path, &disk_key, 1);
1192
1193         BUG_ON(list_empty(&leaf_buf->dirty));
1194         if (btrfs_leaf_free_space(leaf) < 0)
1195                 BUG();
1196         check_leaf(&path, 0);
1197 out:
1198         btrfs_release_path(root, &path);
1199         return ret;
1200 }
1201
1202 /*
1203  * delete the pointer from a given node.
1204  *
1205  * If the delete empties a node, the node is removed from the tree,
1206  * continuing all the way the root if required.  The root is converted into
1207  * a leaf if all the nodes are emptied.
1208  */
1209 static int del_ptr(struct btrfs_root *root, struct btrfs_path *path, int level,
1210                    int slot)
1211 {
1212         struct btrfs_node *node;
1213         struct btrfs_buffer *parent = path->nodes[level];
1214         u32 nritems;
1215         int ret = 0;
1216         int wret;
1217
1218         node = &parent->node;
1219         nritems = btrfs_header_nritems(&node->header);
1220         if (slot != nritems -1) {
1221                 memmove(node->keys + slot, node->keys + slot + 1,
1222                         sizeof(struct btrfs_disk_key) * (nritems - slot - 1));
1223                 memmove(node->blockptrs + slot,
1224                         node->blockptrs + slot + 1,
1225                         sizeof(u64) * (nritems - slot - 1));
1226         }
1227         nritems--;
1228         btrfs_set_header_nritems(&node->header, nritems);
1229         if (nritems == 0 && parent == root->node) {
1230                 BUG_ON(btrfs_header_level(&root->node->node.header) != 1);
1231                 /* just turn the root into a leaf and break */
1232                 btrfs_set_header_level(&root->node->node.header, 0);
1233         } else if (slot == 0) {
1234                 wret = fixup_low_keys(root, path, node->keys, level + 1);
1235                 if (wret)
1236                         ret = wret;
1237         }
1238         BUG_ON(list_empty(&parent->dirty));
1239         return ret;
1240 }
1241
1242 /*
1243  * delete the item at the leaf level in path.  If that empties
1244  * the leaf, remove it from the tree
1245  */
1246 int btrfs_del_item(struct btrfs_root *root, struct btrfs_path *path)
1247 {
1248         int slot;
1249         struct btrfs_leaf *leaf;
1250         struct btrfs_buffer *leaf_buf;
1251         int doff;
1252         int dsize;
1253         int ret = 0;
1254         int wret;
1255         u32 nritems;
1256
1257         leaf_buf = path->nodes[0];
1258         leaf = &leaf_buf->leaf;
1259         slot = path->slots[0];
1260         doff = btrfs_item_offset(leaf->items + slot);
1261         dsize = btrfs_item_size(leaf->items + slot);
1262         nritems = btrfs_header_nritems(&leaf->header);
1263
1264         if (slot != nritems - 1) {
1265                 int i;
1266                 int data_end = leaf_data_end(leaf);
1267                 memmove(leaf->data + data_end + dsize,
1268                         leaf->data + data_end,
1269                         doff - data_end);
1270                 for (i = slot + 1; i < nritems; i++) {
1271                         u16 ioff = btrfs_item_offset(leaf->items + i);
1272                         btrfs_set_item_offset(leaf->items + i, ioff + dsize);
1273                 }
1274                 memmove(leaf->items + slot, leaf->items + slot + 1,
1275                         sizeof(struct btrfs_item) *
1276                         (nritems - slot - 1));
1277         }
1278         btrfs_set_header_nritems(&leaf->header, nritems - 1);
1279         nritems--;
1280         /* delete the leaf if we've emptied it */
1281         if (nritems == 0) {
1282                 if (leaf_buf == root->node) {
1283                         btrfs_set_header_level(&leaf->header, 0);
1284                         BUG_ON(list_empty(&leaf_buf->dirty));
1285                 } else {
1286                         clean_tree_block(root, leaf_buf);
1287                         wret = del_ptr(root, path, 1, path->slots[1]);
1288                         if (wret)
1289                                 ret = wret;
1290                         wret = btrfs_free_extent(root, leaf_buf->blocknr, 1);
1291                         if (wret)
1292                                 ret = wret;
1293                 }
1294         } else {
1295                 int used = leaf_space_used(leaf, 0, nritems);
1296                 if (slot == 0) {
1297                         wret = fixup_low_keys(root, path,
1298                                                    &leaf->items[0].key, 1);
1299                         if (wret)
1300                                 ret = wret;
1301                 }
1302                 BUG_ON(list_empty(&leaf_buf->dirty));
1303
1304                 /* delete the leaf if it is mostly empty */
1305                 if (used < LEAF_DATA_SIZE / 3) {
1306                         /* push_leaf_left fixes the path.
1307                          * make sure the path still points to our leaf
1308                          * for possible call to del_ptr below
1309                          */
1310                         slot = path->slots[1];
1311                         leaf_buf->count++;
1312                         wret = push_leaf_left(root, path, 1);
1313                         if (wret < 0)
1314                                 ret = wret;
1315                         if (path->nodes[0] == leaf_buf &&
1316                             btrfs_header_nritems(&leaf->header)) {
1317                                 wret = push_leaf_right(root, path, 1);
1318                                 if (wret < 0)
1319                                         ret = wret;
1320                         }
1321                         if (btrfs_header_nritems(&leaf->header) == 0) {
1322                                 u64 blocknr = leaf_buf->blocknr;
1323                                 clean_tree_block(root, leaf_buf);
1324                                 wret = del_ptr(root, path, 1, slot);
1325                                 if (wret)
1326                                         ret = wret;
1327                                 btrfs_block_release(root, leaf_buf);
1328                                 wret = btrfs_free_extent(root, blocknr, 1);
1329                                 if (wret)
1330                                         ret = wret;
1331                         } else {
1332                                 btrfs_block_release(root, leaf_buf);
1333                         }
1334                 }
1335         }
1336         return ret;
1337 }
1338
1339 /*
1340  * walk up the tree as far as required to find the next leaf.
1341  * returns 0 if it found something or 1 if there are no greater leaves.
1342  * returns < 0 on io errors.
1343  */
1344 int btrfs_next_leaf(struct btrfs_root *root, struct btrfs_path *path)
1345 {
1346         int slot;
1347         int level = 1;
1348         u64 blocknr;
1349         struct btrfs_buffer *c;
1350         struct btrfs_buffer *next = NULL;
1351
1352         while(level < BTRFS_MAX_LEVEL) {
1353                 if (!path->nodes[level])
1354                         return 1;
1355                 slot = path->slots[level] + 1;
1356                 c = path->nodes[level];
1357                 if (slot >= btrfs_header_nritems(&c->node.header)) {
1358                         level++;
1359                         continue;
1360                 }
1361                 blocknr = btrfs_node_blockptr(&c->node, slot);
1362                 if (next)
1363                         btrfs_block_release(root, next);
1364                 next = read_tree_block(root, blocknr);
1365                 break;
1366         }
1367         path->slots[level] = slot;
1368         while(1) {
1369                 level--;
1370                 c = path->nodes[level];
1371                 btrfs_block_release(root, c);
1372                 path->nodes[level] = next;
1373                 path->slots[level] = 0;
1374                 if (!level)
1375                         break;
1376                 next = read_tree_block(root,
1377                                        btrfs_node_blockptr(&next->node, 0));
1378         }
1379         return 0;
1380 }
1381
1382